#define _CRT_SECURE_NO_WARNINGS
#include<iostream>
using namespace std;
int W, H;
int ans;
int arr[1005][1005];
int main()
{
	cin >> W >> H;
	for (int i = 2; i <= H + 1; i++) {
		for (int j = 2; j <= W + 1; j++) {
			if (arr[i][j] != -1) {
				arr[i][j] = 1;
				arr[i + 2][j] = -1;
				arr[i - 2][j] = -1;
				arr[i][j + 2] = -1;
				arr[i][j - 2] = -1;
				ans++;
			}
		}
	}
	cout << ans << endl;
	return 0;
}

